Currently, a driving scheme of an outdoor compressor of a variable frequency air conditioner is usually that a direct current bus power is achieved by rectifying and filtering an alternating current power, after the direct current bus power is treated by a power factor correction circuit to rectify a power factor of the direct current bus power, the direct current bus power powers an intelligent power module, finally the intelligent power module drives the compressor to operate directly, meanwhile, the signal processing circuit of the variable frequency air conditioner outputs a driving signal to drive the intelligent power module to operate according to corresponding phase current.
In order to protect the compressor from overcurrent, the existed technology provides a compressor current protection circuit, the compressor current protection circuit samples the phase current of the compressor, and controls a switch of the intelligent power module according to the sampled voltage, and can enable the intelligent power module to shut off the output of the phase current when the overcurrent of the compressor is too large, so that the aim of protecting the compressor can be achieved, meanwhile, the intelligent power module can output a fault protection signal to the variable frequency signal processing circuit, and enable the variable frequency signal processing circuit to stop outputting the driving signal according to the fault protection signal, until the phase current of the compressor returns to normal the intelligent power module starts and drives the compressor to work, the intelligent power module also outputs the fault cancel signal to the signal processing circuit simultaneously, so that, the signal processing circuit can output the driving signal again to drive the intelligent power module to operate normally.
However, during a period of shutting off the intelligent power module, although the signal processing circuit already stops outputting the driving signal, while if a strong interference signal exists on the drive signal line between the signal processing circuit and the intelligent power module, the intelligent power module will output a large current or be damaged, thereby the compressor cannot be protected effectively.
In conclusion, the existed technology, during the overcurrent protection process of the compressor, as the strong interference signal exists on the drive signal line between the signal processing circuit and the intelligent power module, the compressor cannot be effectively protected.